(CNN) - On Sunday, pastor Jim Garlow of Skyline Church in California stood before his congregation of more than 2,000 and told them he would be making an unusual announcement.

The pastor proceeded to warn his audience against voting for a candidate in the upcoming midterm elections who supports gay marriage and abortion, even if that candidate, Carl DeMaio, is a Republican.

Garlow, an outspoken evangelical who played a major role in organizing Christian groups in support of California’s anti-gay marriage Proposition 8, spoke plainly: He would not be supporting the Republican in this race.

“I know enough that you cannot have the advancing of the radical homosexual agenda and religious liberty at the same time, in the same nation,” he preached. “One will win, and one will lose.”

Instead, Garlow told his followers he would be endorsing DeMaio’s rival, Democratic incumbent Scott Peters, representative for California’s 52nd District, to send a scathing message to Republican leadership that candidates who back abortion and gay rights are unacceptable to the party’s Christian base.

The CNN Belief Blog covers the faith angles of the day's biggest stories, from breaking news to politics to entertainment, fostering a global conversation about the role of religion and belief in readers' lives. It's edited by CNN's Daniel Burke with contributions from Eric Marrapodi and CNN's worldwide news gathering team.